1. Field
Embodiments of the present invention relate to membrane filtration systems and, more particularly, to an improved cleaning method and apparatus for such systems.
2. Description of Related Art
The use of membrane filtration systems is rapidly growing. The success of such systems largely depends on employing effective and efficient membrane cleaning methods. Commonly used physical cleaning methods include backwash (e.g., back pulse, back flush) using liquid permeate or a gas, and membrane scrubbing or scouring using a gas in the form of bubbles in a liquid. Examples of this second type of method are generally described in U.S. Pat. No. 5,192,456 to Ishida et al.; U.S. Pat. No. 5,248,424 to Cote et al.; U.S. Pat. No. 5,639,373 to Henshaw et al.; U.S. Pat. No. 5,783,083 to Henshaw et al.; and International Patent Application Publication Nos. WO98/28066 and WO00/18498 (assigned to the Applicant).
These conventional methods use a variety of techniques to introduce gas bubbles into the membrane arrays to produce effective and efficient surface cleaning Effective cleaning can be achieved by introducing bubbles into the array in a uniform manner—as much as possible to produce efficient cleaning of the membrane surfaces.
Some filtration systems include a bundle of fibre membranes mounted in a generally vertical orientation between spaced upper and lower headers with bubbles flowing from below the lower header or formed by flowing gas or a gas/liquid mixture through openings in the lower header. A filtration system of this variety is illustrated in FIG. 1.
The use of openings in the lower header complicates the potting process of fibres in the lower header and can lead to breakage of the fibres in the region of the openings, as well as limitations on the packing density of the fibres within the header.